Abstract: 【Objective】The difference of nutrient release curves of controlled release urea coated by vegetable oil (PCU) obtained by both in the soil incubation at four growing stages of banana and that in still pure water dissolving incubation was studied in order to prove whether still pure water dissolving incubation method being a simple method to forecast the nutrient supplying rate and amount of the PCU in the soil at different growing stages.【Method】The cumulative nutrients release rate and longevity of the PCU were determined by using soil incubation method taking the still pure water dissolving incubation method as check. The nutrient release characteristics of the PCU at four growing stages during banana growth were measured, respectively.【Result】The nutrient accumulation release curve of the PCU in the soil was different from that obtained by pure water dissolving incubation method. Except for the bud promotion stage the curves at the field seedling stage, the fast growth stage and the young fruit stage changed into “parabolic” pattern from the “sigmoid” one in the water. Within the first 42 days of incubation, the nutrient supply amount of the PCU at all of the three stages was greater while which was smaller at the bud promotion stage and it was in adverse after 42 days. The initial release rate, differential release rate and cumulative release rate of 28 days of the same PCU in the soil was bigger than those in still pure water dissolving incubation, respectively. The initial release rate was in order of the fast growth stage＞the young fruit stage≥the field seedling stage＞the bud promotion stage during banana growth. The differential release rate was in order of the field seedling stage＞the young fruit stage＞the bud promotion stage=the fast growth stage. The volume of cumulative release rate of 28 days was in order of the young fruit stage＞the field seedling stage=the fast growth stage＞the bud promotion stage. Compared with the result measured by still pure water dissolving incubation method, the longevity of the PCU in the soil applied at both of the field seedling stage and the fast growth stage was extended by 18 days and 35 days, respectively, while the longevity at the bud promotion stage and the young fruit stage was shorten by 10 days and 30 days, respectively.【Conclusion】When the same kind of controlled release urea was applied at different growing stages during banana growth, the nutrient supply of the PCU were different at each stage in the same time. The nutrient supply of the PCU was a big amount in prophase when it was applied at the field seedling stage, the fast growth stage and the young fruit stage, respectively, while that was small in later period at those stages. Nevertheless, the nutrient supply of the PCU was a small amount in prophase when it was applied at the bud promotion stage, while that was big in later period at this stage.

Key words: controlled release urea coated by vegetable oil (PCU) , banana growing stage , release rate in water , release rate in soil , nutrient release characteristics